Motor control system



Mrch 13, 1934. w s r AL 1,951,225

MOTOR CONTROL S YSTEM Filed March 13. 1928 Inventohs: Paul \A/eisKe, Konrad Rupphecht,

by WKZZM Theiw Attorney Patented Mar. 13, 1934 UNITED STATES PATT OFFICE MOTOR CONTROL SYSTEM Application March 13, 1928, Serial No. 261,377 In Germany March 23, 1927 21 Claims.

With the drive of wood grinders especially in the case of a common drive for several grinders, it has been hitherto customary to regulate the speed of the feed motors and thereby the load or" the grinders in dependence on the energy consumption or speed of the prime mover driving the stone. The regulating device has the function of keeping as constant as possible the energy consumption or speed of the driving machine. For the feed drives either a common regulating de-- vice or one for each drive has been provided, for example, throttle valves, regulating resistances, etc., by means or" which in case of fluctuations oi the load or speed of the driving machine all the feed .drives are influenced simultaneously and uniformly or in adjustable relation. The speed or load of the feed drives, however, does not give any reliable solution as regards the strength of pressure of the wood against the stones, because the supply of wood is often hampered by jamming or other irregularities. If such disturbances ocour in individual grinders then through the regulating device the pressure in the other grinders is increased in a corresponding degree. In this way, the load or speed of the driving machine can be kept constant in a certain measure. Through the increased pressure however a very irregular coarse grinding is produced.

At the present time, however, wood grinding of such quality and uniformity has been required that it would be possible to use it immediately for manufacturing paper without the hitherto usual subsequent refining operation. In order to effect this, according to the invention the loading of the wood grinders is regulated in dependence on the pressure of the wood acting on the stone and not as hitherto in dependence on the load or speed of the driving me chine. Specially suitable constructions are obtained ii" the regulation is effected in dependence on the pressure fluctuations exerted on the lower bearing brasses of the grinder shafts. In that case, for example, slots can be provided in the lower bearing bra-sees of the grinder shafts which ar connected by means of conduits with pressure gauges whose movable members act on regulating members such as valves, regulating resistances or the like provided for regulating the wood supply. If there are several grinders coupled with one another driven in common, then the load of each individual grinder will be constantly regulated uniformly independently of that of the other grinders to a predetermined value in dependence on the variations of the pressure of the wood on the grind stone.

The invention starts from the perception that the pressure of the grinder shaft on the lower bearing brasses varies in accordance with the pressure of the wood against the stone, and, further, when flexible couplings between the individual grinder shafts are used, the pressure on the bearing surface is independent of the torque transmitted by the grinder shaft onto the succeeding grinders. Thus the pressure transmitted onto the lower bearing brasses oi the grinder shaft is a reliable standard for the load of each of the individual grinders driven in common.

In the drawing, a constructional example of the invention is diagrammatically represented.

The drawing shows several grinders coupled together and driven in common, while the pressure on the bearing surface of the grinder shafts is measured in a very simple manner and is utilized for influencing the wood feed regulation. The shafts of the grind-stones 1, 2 and 3 are connected with one another and with the driving machine or motor 4 by means of flexible couplings 5, 6 and '7. The lower bearing brasses 8, 9; 10, 11 and 12, 13 of the grinders 1, 2 and 3, respectively, are each provided with a special slot in which the oil for the bearing is stored, these slots in the bearings 8 to 13, inclusive, being indicated by the reference characters 8 to 13 inclusive. The slots of the bearings belonging to a particular grinder are connected with a pressure responsive device or gauge by means of conduits. The oil pressure in the slots of the lower bearing brasses is varied correspondingly with the pressures of the wood pressing down on the grind-stones, as indicated in the drawing by arrows P. Variations of these pressures effeet a corresponding movement of the movable member at the pressure gauge, for example, of the diaphragm 14 to which the slots 8 and 9 are connected through conduits 15 and 16. This movable member at the pressure auge may also be a control piston 1'? which is shown connected through conduits l8 and 19 to the slots 10 and 11 or the pressure gauge may be any other suitable device which is adjusted by means of a spring or in a similar manner, and transmits its movement to the regulating member of the associated feed motor. For example, the feed motor for the grind-stone 1 may be regulated by means of a throttle valve 20, and the feed 10 motor in this instance may be a steam engine. The feed motor may also be an electric motor and, as shown, the control piston 17 is connected to a regulating resistance 21 of an electric feed motor for the grind-stone 2. In a similar man- 116 her, the slots 12 and 13 in the bearings of the grind-stone 3 will be connected through conduits 22 and 23 to suitable pressure responsive control means for the feed motor of grind-stone 3. Preferably, the feed motors will be all three of the same general type, i. e., steam engines, electric motors, etc.

Obviously, any suitable means may be used for controlling the speed of the feed motors through the agency of regulating resistances 21. In the specific control means shown in connection with the grindstone 2 the regulating resistance 21 is connected by the conductor 26 in an electric circuit with the field winding 27 of a generator G which in turn is permanently connected in a Ward Leonard system to the feed motor M for the grindstone 2.

In this manner the speed of each feed motor is diminished in the case of a too great increase of its particular grinder load and is increased with the lowering of the grinder load. The grinder load which is to be kept constant for the time being can be conveniently adjusted at any time by means of a spring load working in opposition to the bearing oil pressure. Such springs, 24 and 25, are shown in connection with the pressure responsive devices 14 and 17.

The arrangement can obviously be constructed otherwiseif desired, for example, in such manner that the bearings of the grinder shafts rest on flexible supports, for example, pressure liquid or spring supports, which, in the case of variations of pressure of the wood on the grindstone, influence correspondingly the regulating member for the feed motor.

It is possible to apply the subject of the invention to all kinds of grinders, particularly when the Wood is pressed mainly against the stones from above, as well as to various other machines. Moreover, it is entirely immaterial whether the drive of the grinder shafts is effected by means of an electric motor, steam engine or another prime mover.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. The combination with a grinding device provided with bearings, of recesses for a fluid in said bearings, a pressure responsive device, conduits connecting said recesses with said pressure responsive device, a feed motor for said grinding device, and control means for said motor operated by said pressure responsive device so as to maintain a substantially constant load on said grinding device.

2. The combination with a grinding machine or the like provided with a rotary Working element and a supporting shaft therefor, of a bearing for said shaft providing for limited radial movement of said shaft in dependence upon pressure applied to said working element, means for feeding material against said working element, a motor for driving said feeding means, pressure responsive means connected with said shaft so as to be actuated by said radial movement, and control means for said motor actuated by said pressure responsive means to feed the material to said working element so as to maintain a substantially constant pressure on said bearing.

3. The combination with a plurality of grinding machines or the like, each provided with a supporting shaft, said shafts being arranged in alignment with each other, a flexible driving con nection between said shafts, a common driving motor connected to said shafts, a bearing for each of said shafts providing for limited radial movement thereof in response to pressure on its respective grinding machine, said pressure varying with the rate of feed of material to said grinding machine, a pressure responsive device connected to each of said shafts so as to be actuated by the radial movement thereof, feeding means for each of said grinding machines, a driving motor for each of said feeding means, and control means for each of said driving motors actuated by the pressure responsive device for the respective grinding machine so as to maintain substantially constant pressures on said bearings.

4. The combination with a machine for performing a predetermined operation on material supplied thereto, said machine being provided with a working element, a bearing for said working element subjected to a pressure varying with the rate of feed of the material to said machine, a lubricant for said bearing subjected to said pressure, means for feeding the material to said machine, and means responsive to the pressure in said lubricant for controlling said feeding means.

5. The combination with a grinding machine or the like provided with a grinding element and a bearing for said grinding element provided with a lubricant subjected to a pressure applied thereto by said grinding element varying with the rate of feed of the material to said machine, of means for feeding material to said machine, a driving motor for said feeding means, and means responsive to the pressure in said lubricant for controlling said motor so as to vary the rate of speed of the material to said machine and thereby maintain a substantially constant pressure in said lubricant.

6. The combination with a grinding machine or the like provided with a grinding element and a bearing therefor provided with a lubricant subjected to a pressure applied by said grinding element varying with the rate of feed of the material to said machine, of means for feeding the material to said machine, a fluid pressure responsive device for controlling said feeding means, and a conduit connection between said pressure responsive device and said lubricant whereby said device is responsive to the lubricant pressure in said bearing.

'7. The combination in a wood grinding ma chine, of a grindstone, a shaft and a bearing therefor, means for feeding the wood against said grindstone to apply a pressure thereto, an oil film between said shaft and said bearing subjected to said pressure, and means responsive to variations in pressure in said oil film for controlling said feeding means so as to feed the wood against said grindstone with a substantially constant pressure.

8. The combination in a wood grinding ma chine of a plurality of grindstones connected to a common driving shaft, a driving motor for said shaft, separate bearings for said shaft for each grindstone, means for feeding the wood against each grindstone to apply a pressure thereto, an oil film between said shaft and each of said bearings subjected to the pressures on the respective grindstones, pressure responsive means for each of said grindstone connected through conduit means to the bearings of the respective grindstones so as to be subjected to said pressure and driving means for said feeding means controlled by said pressure responsive means so as to maintain a substantially constant pressure on each of said grindtones.

9. In a wood grinder, the combination of a grindstone, its carrying shaft and bearings therefor, means for feeding'the wood against the stone to exert pressure thereon, an oil film between the shaft and. its bearings subject to said pressure, and means controlled by variations of the pressure of the oil film for controlling the feed of the wood.

10. In a wood grinder, the combination of a grindstone, its carrying shaft and bearings, means for feeding wood against the stone to exert pressure thereon, an oil film between the shaft and its bearings subject to said pressure, and means actuated by an increase of the pressure of said oil film to reduce the pressure of the wood against the stone.

11. In a wood grinder, the combination of a grindstone, its carrying shaft and bearings, means for feeding the wood against the stone to exert pressure thereon, an oil film between the shaft and its bearings subject to said pressure, and means actuated by a decrease of the pressure of said oil film to increase the pressure of the wood against the stone.

12. In a wood grinder, the combination of a grindstone, its carrying shaft and bearings, means for feeding wood against the stone to exert pressure thereon, an oil film between the shaft and its bearings subject to said pressure, means ac tuated by an increase of pressure of said oil film to decrease the pressure of the Wood against the stone, and acting on a decrease of the pressure of the oil film to increase the pressure of the wood against the stone.

13. In a wood grinding machine, the combination of a grindstone, its carrying shaft and bearings, means for feeding the wood against the stone to exert pressure thereon, an oil film between the shaft and its bearings subject to said pressure, a movable element responsive to the pressure of said oil film, and electric means for controlling the action of the wood feeding means, said electric means including an electric circuit adapted to be controlled by said pressure responsive element.

14. In a wood grinder, the combination of a grindstone, its carrying shaft and bearings therefor, said bearings providing for limited radial movement of said stone and shaft, means for feeding the wood against the stone, whereby the stone and shaft will be subjected to pressure acting to move them radially varying degrees in accordance with the variations of pressure of the wood against the stone, and control means for said wood feeding means connected to said shaft so as to be actuated by the said radial movements on an increase of said pressure and thereby vary the action of the wood feeding means to reduce the pressure of the wood on the stone.

15. In a wood grinder, the combination of a grindstone, its carrying shaft and bearings therefor, said bearings providing for limited radial movement of said stone and shaft, means for feeding the wood against the stone, whereby the stone and shaft will be subjected to pressure acting to move them radially varying degrees in accordance with variations of pressure of the wood against the stone, and control means for said wood feeding means connected to said shaft so as to be actuated by the radial movements on a decrease of said pressure, and thereby vary the action of the wood feeding means to increase the pressure of the wood on the stone.

16. In a wood grinder, the combination of a grindstone, its carrying shaft and bearings therefor, said bearings providing for limited radial movement of said stone and shaft, means for feeding the wood against the stone, whereby the stone and its shaft will be subjected to pressure acting to move them radially varying degrees in accordance with the variations of pressure of the wood against the stone, and controlling meansfor said wood feeding means connected to said shaft so as to be actuated by said radial movements on an increase of said pressure to vary the action of the wood feeding means to reduce the pressure of the wood against the stone, and actuated by said radial movements on a decrease of said pressure to vary the action of the wood feeding means to increase the pressure of the wood against the stone.

1']. In a wood grinder, the combination of a grindstone, its carrying shaft and bearings therefor, said bearings providing for limited radial movement of said stone and shaft, means for feeding the wood against the stone, whereby the stone and consequently the shaft will be subjected to pressure acting to move them radially varying degrees in accordance with the variations of pressure of the wood against the stone, and control means for said feeding means connected to said shaft so as to be operated automatically by said radial movements to vary the speed of the feeding means.

18. In a wood grinder the combination of a grindstone, its carrying shaft and bearings therefor, said bearings providing for limited radial movement of said stone and shaft, means for feeding the wood against the stone, whereby the stone and consequently its shaft will be subjected to pressure acting to move them radially varying degrees in accordance with the variations of pressure of the Wood against the stone, and control means for said feeding means connected to said shaft so as to be operated automatically by said radial movements to decrease the speed of the wood feeding means on an increase of said pressure, and to increase the speed of the feeding means on a decrease of said pressure.

19. In a wood grinder, the combination of a grindstone, its carrying shaft and bearings therefor, said bearings providing for limited radial movement of said stone and shaft, means for feeding the wood against the stone, whereby the stone and consequently its carrying shaft will be subjected to pressure acting to move them radially different degrees in accordance with the variations of the pressure of the wood against the stone, an electric motor for operating the wood feeding means, a movable element connected to said shaft so as to be responsive to said radial movements, and electric means connected to said element so as to be movable thereby to vary the speed of said motor.

20. In a wood grinder, the combination of a grindstone, its carrying shaft and bearings therefor, said bearings providing for limited radial movement of said stone and shaft, means for feeding the wood against the stone, whereby the stone and its carrying shaft will be subjected to pressure acting to move them radially varying degrees according to the variations of pressure of the wood against the stone, an electric motor for driving the feeding means, a movable element connected to said shaft so as to be responsive to said radial movements, electric means connected to said movable element for controllingsaid motor and operating when said movable element is moved to one position to speed up the motor, and when moved to another position to slow down the motor.

21. The combination with a grinding device provided witha supporting shaft, a bearing for said shaft provided with a recess for containing a portion of the lubricant in said bearing, said recess being positioned between the ends of said bearing in a lower region thereof so as to be closed by said shaft, a pressure responsive device, a conduit connecting said recess with said pressure responsive device, a motor for feeding material PAUL WEISKE. KONRAD RUPPRECHT. 

